Abstract
Laser-enhanced ionization (LEI) spectroscopy is presently being utilized for the analysis of trace metals in a variety of samples. The measurement is usually performed in the traditional analytical air-acetylene flame. This flame is well suited to LEI, serving not only as the source of sample atomization, but also as the source of collisional ionization of the excited analyte atoms produced by resonant laser excitation. However, the flame does have weaknesses which limit the usefulness of LEI. Many elements are not efficiently atomized, and a variety of chemical interferences, well known in conventional flame spectroscopy, occur in LEI as well. Interfering molecular spectra from flame molecules are also observed. Many analytical methodologies have largely abandoned the flame for higher temperature electrical plasmas, notably the atmospheric pressure argon inductively coupled plasma (ICP). The inert argon atmosphere and higher temperature of the ICP ensure a more complete atomization of most elements and a relative freedom from chemical interference. Such advantages would also benefit LEI measurements, if LEI could be performed in an ICP, but very high electron densities and radio-frequency (rf) interference from the plasma power source make sensitive detection of LEI in a conventional ICP impossible.
© 1990 Optical Society of America
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